Cytokines are stimulators of the immune system and are thus useful as drugs. For example, interferon-alpha (IFN-α), interferon-beta (IFN-β), interleukin-2 (IL-2), and granulocyte/macrophage-colony stimulating factor (GM-CSF) are all approved drugs used to treat viral infections, cancer, immune system misregulation such as autoimmune disease, and to promote recovery of the immune system after cancer chemotherapy. Unfortunately, these proteins can stimulate an immune response against themselves, causing patients to develop antibodies against the therapeutic protein. These antibodies can also inhibit function of the same protein endogenously produced within the patient, resulting in potential long-term consequences for patient health.
Interleukin-7 is a cytokine that promotes survival and proliferation of T-cells, B-cells, and other immune cells. It is also potentially a therapeutic protein to treat patients whose immune systems have been damaged by cancer chemotherapy, HIV infection, or other diseases, disorders, or chemical exposures. However, based on its immunostimulatory properties, therapeutically administered IL-7 is expected to induce an antibody response against itself. Therefore, there is a need in the art for improved versions of IL-7 that are less immunogenic, but that retain the property of stimulating the immune system.